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What should I do about the sulfation of lead-acid battery plates?

by:dcfpower     2021-03-17

The so-called sulfation refers to the formation of irreversible lead sulfate on the positive and negative plates of lead-acid batteries to form a layer of white coarse-grained crystalline lead sulfate. This kind of crystal is difficult to eliminate during normal charging. The degree of sulfation formation has a great relationship with the capacity of the lead-acid battery. The more serious the sulfidation, the less the capacitance, until it is scrapped. There are many factors for the sulfation of the plate, mainly The storage time of lead-acid batteries is too long because of the presence of sulfuric acid on the surface of the active material during chemical conversion treatment, which causes the lead sulfate on the surface of the active material to lose its ionization effect. When the battery is charged, the electrolyte density is too high or impure, and the surface of the active material in the positive and negative plates will not be vulcanized. Therefore, sulfation is the main reason for the invalidation of the active material of the plate.

(1) The phenomenon of plate sulfation is as follows:

1 When discharging, the capacity of sulfated battery is significantly lower than that of other normal batteries .

2 The electrolyte density has fallen below the normal value, and it is a long-term lag.

3 During the charging process, the voltage rises quickly, up to about 2.9 volts/cell (the normal value is about 2.7 volts/cell), and the voltage drops quickly during the discharging process, which can be completed within 1 to 2 hours. Reduce to about 1.8 volts (10-hour rate discharge).

4Bubbling is premature during charging.

The color and state of the 5 plate are abnormal. The positive plate is light brown (normally dark brown), there are white lead sulfate spots on the surface of the plate, and the negative plate is off-white (normally gray). When you touch the surface of the plate with your fingers, you feel that there are coarse lead sulfate crystals, and the plate Stiff.

(2) Treatment method for sulfation of lead-acid battery plate

1 Overcharge method. It is suitable for storage batteries that are not very sulfated.

Pour out the electrolyte in the battery and immediately add pure water, the liquid level is about 20mm higher than the electrode plate, use 0.1C20A for charging (C20 is the rated capacity of the battery).

When the voltage rises to 2.5V/single cell, stop charging for half an hour, switch to 0.025C20A low current charge for several days and nights (over 100 hours) until the voltage, specific gravity, etc. remain stable, and the plate is white Until the spots disappear. Adjust the electrolyte density to 1.28g/ml 1 hour before stopping charging.

2 Repeated charging method. Sulfation is serious, and the capacity is only half of the normal battery. Pour out the electrolyte and immediately add pure water, the liquid level is about 20mm higher than the electrode plate.

When charging with 0.1C20A current, when the voltage rises to 2.5V/div, stop charging for half an hour, switch to 0.05C20A current charging and stop charging for half an hour when there are large bubbles, switch to 0.05C20A charging When the voltage, density, etc. remain stable, stop charging for half an hour, and then re-energize, the electrolyte will immediately boil, and the voltage will rise to the value at the end of the last charge in about 10 minutes, otherwise stop recharging.

The charged battery is discharged with a current of 0.05C20A. When the voltage is 1.80V/div, the battery should be parked for 1~2 hours and then charged with a current of 0.05C20A. After the battery is charged, discharge it again, such as the capacity. If the white spots have not been improved, charge and discharge again. Repeat for several days and nights until the discharge is close to the rated capacity and the white spots are completely eliminated.

3 Hydrotherapy (repeated charge and discharge method). It is suitable for batteries whose sulfation is extremely serious and whose capacity has not reached half of the rated capacity.

Discharge the battery to a voltage of 1.8 volts/div (with a 10-hour rate current), pour out the electrolyte and inject pure water, the liquid level is about 20mm higher than the plate, and let it stand for 1~2 hours , Use 0.05C20A to charge until the electrolyte density rises to 1.1~1.2g/m1, switch to 0.02C20A to charge until the electrolyte density no longer rises, and air bubbles uniformly, discharge with 0.02C20A for 2 hours. Then charge it with 0.02C20A until bubbles evenly appear. Note that the charged power should far exceed the discharged power. Repeat this for several weeks or one month until 0.05C2 is used. The discharge inspection reaches more than 75% of the rated capacity.

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